1. Field of the Invention
The invention generally relates to adapative communication systems and, in particular, to an adaptive communication receiving unit suitable for the suppression of noise and jamming signals; which receiving unit comprises:
a plurality of antenna elements; PA1 a network of adaptive weighting filters connected to the antenna elements; PA1 a combination circuit connected to the networks; PA1 a detector connected to the combination circuit and provided with means for generating a replica (d) of the information-supplying carrier signal and with means for demodulating the signal (y) of the combination circuit to the information-related frequency band on the basis of the replica (d); and PA1 adjusting means for generating adjustment signals for the adaptive weighting filters. PA1 a signal measurement per weighting filter; PA1 the calculation of a weighting factor per weighting filter by the adjusting means according to an algorithm adapted to an optimal transmission characteristic; PA1 the generation of a beam-steering command in the form of adjustment signals by the adjusting means on the basis of the calculated weighting factors for the weighting filters.
The signal produced by the combination circuit consists of three components obtained from the information-carrying communication signal, the jamming signal and the noise.
2. Description of the Prior Art
A receiving unit of the type as set forth in the opening paragraph is known from the article entitled "Adaptive Antenna Systems", by B. Widrow, P. R. Mantey, L. J. Griffiths and B. B. Goode, Proceedings of the IEEE, Vol. 55, 1967, pp. 2143-2159. The communication receiving unit described in this article is designed on a transmission characteristic of the combination of antenna elements, weighting filters and combination circuit, which combination is optimal in respect of the signal distortion; such a receiving unit has an antenna pattern with a relatively low sensitivity in the direction of the jammer and a relatively high sensitivity in the direction of the communication transmission unit. For this reason, an iterative process is performed in the receiving unit, comprising the steps of:
With such a communication receiving unit the signals are however measured on a radio-frequency level; this gives rise to problems with respect to the phase synchronisation between the various signals, the broadband performance of the adjusting means, the dynamics of the receiving part subjected to the signal measurement, and the associated hardware complexity of this part.